The retrovirus designated human immunodeficiency virus (HIV), particularly the strains known as HIV type-1 (HIV-1) and type-2 (HIV-2), have been etiologically linked to the immunosuppressive disease known as acquired immunodeficiency syndrome (AIDS). HIV seropositive individuals are initially asymptomatic but typically develop AIDS related complex (ARC) followed by AIDS. Affected individuals exhibit severe immunosuppression which makes them highly susceptible to debilitating and ultimately fatal opportunistic infections. Replication of HIV by a host cell requires integration of the viral genome into the host cell's DNA. Since HIV is a retrovirus, the HIV replication cycle requires transcription of the viral RNA genome into DNA via an enzyme known as reverse transcriptase (RT).
Reverse transcriptase has three known enzymatic functions: The enzyme acts as an RNA-dependent DNA polymerase, as a ribonuclease, and as a DNA-dependent DNA polymerase. In its role as an RNA-dependent DNA polymerase, RT transcribes a single-stranded DNA copy of the viral RNA. As a ribonuclease, RT destroys the original viral RNA and frees the DNA just produced from the original RNA. And as a DNA-dependent DNA polymerase, RT makes a second, complementary DNA strand using the first DNA strand as a template. The two strands form double-stranded DNA, which is integrated into the host cell's genome by the integrase enzyme.
It is known that compounds that inhibit enzymatic functions of HIV RT will inhibit HIV replication in infected cells. These compounds are useful in the prophylaxis or treatment of HIV infection in humans. Among the compounds approved for use in treating HIV infection and AIDS are the RT inhibitors 3′-azido-3′-deoxythymidine (AZT), 2′,3′-dideoxyinosine (ddI), 2′,3′-dideoxycytidine (ddC), d4T, 3TC, nevirapine, delavirdine, efavirenz, abacavir, emtricitabine, and tenofovir. Current standard of care is to employ highly active anti-retroviral therapy (HAART). HAART therapy is defined as the combination of 3 agents from at least 2 different mechanistic classes. While HAART based treatment regimens employing RT inhibitors are effective in treating HIV infection and AIDS, there remains a need to develop additional HIV antiviral drugs including additional RT inhibitors. A particular problem is the development of mutant HIV strains that are resistant to the known inhibitors. The use of RT inhibitors to treat AIDS often leads to viruses that are less sensitive to the inhibitors. This resistance is typically the result of mutations that occur in the reverse transcriptase segment of the pol gene. The continued use of antiviral compounds to treat HIV infection will inevitably result in the emergence of new resistant strains of HIV. Accordingly, there is a particular need for new RT inhibitors that are effective against mutant HIV strains.
WO 2009/067166 and WO 2011/126969 disclose certain RT inhibitors prodrugs. Clemo et al., J. Chem. Soc. 1954, pp. 2693-2702 discloses certain derivatives of the 4-oxo-3-(2-pyridyl)pyridocoline system and in particular discloses 6-methyl-6′-phenoxy-2,2′-methylenedipyridine. Sweeney et al., Bioorganic & Medicinal Chem. Letters 2008, vol. 18, pp. 4348-4351 discloses a series of triazolinones that were found to be non-nucleoside inhibitors of HIV reverse transcriptase. WO 2001/034578 discloses certain substituted azoles (including, for example, certain imidazoles and benzimidazoles) having anti-Helicobacter pylori activity. In particular, WO '578 discloses 1-[(3-methyl-4-phenoxy-2-pyridinyl)methyl]-1H-benzimidazole (see Compound 91 on page 40). WO 2004/085406 and corresponding U.S. Pat. No. 7,189,718 disclose certain benzyl pyridazinones as reverse transcriptase inhibitors. WO 2005/102989 and corresponding U.S. Pat. No. 7,166,738 disclose certain N-phenyl 2-phenylacetamides to be non-nucleoside reverse transcriptase inhibitors. WO 2006/067587 discloses certain biaryl ether derivatives to be modulators of the reverse transcriptase enzyme. WO 2007/045572 and WO 2007/045573 disclose certain 2-(2-phenoxyphenyl) N-phenyl acetamides as non-nucleoside reverse transcriptase inhibitors. WO 2008/076225 discloses certain indazoles, benzotriazoles and related bicyclic compounds as HIV reverse transcriptase inhibitors. WO 2009/067166 discloses certain aryloxy-, cycloalkyloxy-, and heterocyclyloxy-pyridines and related compounds. The compounds are HIV reverse transcriptase inhibitors suitable, for example, for the treatment of infection by HIV. Among the compounds disclosed are certain 3-(3,5-disubstituted phenoxy)-1-(1H-pyrazolo[3,4-b]pyridin-3-ylmethyl)-4-(substituted)pyridin-2(1H)-ones. US 2004/0192704 discloses certain 3-(phenoxy)benzyl substituted 5-membered triazolones, oxadiazolones, and thiadiazolones. The compounds are disclosed to be non-nucleoside reverse transcriptase inhibitors useful for the treatment or prophylaxis of HIV mediated diseases. US 2007/0021442 and WO 2007/015812 disclose certain substituted aromatic compounds. The compounds are HIV reverse transcriptase inhibitors suitable, for example, for the treatment of infection by HIV. WO 2009/067166 and WO2011/120133 discloses HIV non-nucleoside reverse transcriptase inhibitors. WO 2011/126969 discloses prodrugs of HIV non-nucleoside reverse transcriptase inhibitors